Effect of calcium, magnesium, and cytochalasin B on arachidonic acid-induced neutrophil aggregation.

Suspended in media containing calcium and magnesium, human neutrophils aggregate briefly when exposed to arachidonic acid. The magnitude and duration of this response was enhanced by the presence of increased magnesium concentration, increased magnesium plus calcium concentrations, and cytochalasin B. The response was inhibited by increased calcium concentrations. When calcium, magnesium, or both bivalent cations were omitted from the cell suspension, the response did not occur. Since various chemotatic factors also briefly aggregate neutrophils and since these chemotatic factor-induced responses are similarly influenced by the bivalent cations and cytochalasin B, a close association between the bioactivities of arachidonic acid and chemotactic factors is evident. The aggregation response to both types of stimuli may share common intracellular mechanisms.